After 340 days in space, astronaut Scott Kelly has set the US record for most consecutive days in space.

The astronaut was there to help NASA study the effects of long-term space travel. This data is needed if NASA ever develops a manned mission to Mars or other far-reaching planets. Some effects could be the weakness of bone density or the loss of vision.

The White House released a statement saying, “Kelly’s year in space would provide critical data to researchers trying to understand how to keep astronauts healthy during long space voyages and fulfill the President’s vision of putting American astronauts on Mars in the 2030s.”

Physically, Kelly says that he feels fine, and at first, there seemed to have been no major effects. However, initial measurements showed that he had actually grown one and a half inches while in space. But after only two days of returning, he had shrunk back to his normal height.

Kelly told reporters in his last interview in space, “I could go for another 100 days or 100 years.”

The 52 year old astronaut made the return journey on Tuesday, accompanied by Russian Cosmonauts, Mikhail Kornienko and Sergey Volkov. The trio landed in the Kazakhstan Dessert aboard the Russian, Soyuz spacecraft.

Kelly told CNN, “The hardest part is being isolated from people on the ground who are important to you.”

He also went on the talk about the Earth’s environment saying, “I feel like an environmentalist since I’ve been up here. There are parts of the Earth that are covered with pollution all the time. I saw weather that was unexpected. Storms bigger than we’ve seen in the past. This is human effect. This is not a natural phenomenon.”

He also said that the Earth’s atmosphere, “looks very, very fragile” and that “If we can dream it, we can make it possible (fixing the environment).”

In a separate CNN interview, Kelly told Doctor Sanjay Gupta, “”I’ll probably never see it again. I’ve flown in space four times now, so it’s going to be hard in that respect, but I certainly look forward to going back to Earth. I’ve been up here for a really long time and sometimes, when I think about it, I feel like I’ve lived my whole life up here.”

Kelly visited his family and friends to whom he had attributed his success in space.

Kelly told reporters, “It’s great to be back in Texas, on U.S. soil … on planet Earth. This is not my achievement. It’s NASA’s achievement and it’s our country’s achievement. There’s no greater privilege than serving your country however and wherever you might do it.”

Kelly celebrated his return with a plunge in his swimming pool, full astronaut suit and all.